Equally, though, if the shake were due to shutter shock, it should be just as 'fixed' with 2 second anti-shock as it is with 1/8 second. In practice, 2 second anti-shock gives just as much shake as 2 second self-timer. That's difficult for me to fit with a shutter shock explanation.

At this point, while there are certainly other tests which could be done to try to pin things down, it starts to look like a lot of time spent for minimal benefit. What matters here are the two simple observations - the E-P5 seems unusually prone to producing blurred images, and the anti-shake setting looks like an option worth trying for users who notice this and consider it a problem.

Andy,

Both self-timer and "anti-shock" lag could not help against shock occurring DURING exposure, when the first curtain comes to hard stop.

Anti-shock could counteract initial closing of the shutter, self-timer could help against hard pressing on the button.